1. Field of the Invention
The invention relates to a protective device applied to an electronic device, and in particular a protective device capable of preventing over currents and over voltages.
2. Description of Related Art
In recent years, due to booming development of information technology (IT), IT products such as cell phones, computers and personal digital assistants are commonplace. With their help, demands in various aspects such as food, clothing, housing, travelling, education, and entertainment are met, and people increasingly dependent on IT products. However, lately, there has been news about exploding batteries of portable electronic products during charging and discharging. Hence, the industry has enhanced protective measures used during charging and discharging of batteries, so as to prevent explosions of batteries during charging and discharging because of over voltages or over currents.
According to a protection method of the protective device provided by the conventional technique, a temperature fuse in the protective device is serially connected with a circuit of a battery, and the temperature fuse in the protective device and a heater are electrically connected to controlling units such as a field effect transistor (FET) and an integrated circuit (IC). In this way, when the IC senses an over voltage, it drives the FET, so that a current passes through the heater which heats up to melt the temperature fuse, thereby making the circuit of the battery disconnected and achieving protection from over voltages. In addition, when an over current occurs, the massive current flows through the temperature fuse, thereby melting the temperature fuse, so that the circuit of the battery is disconnected to achieve the purpose of protection against over currents.